1. Field of the Invention
The present disclosure relates to the prevention and/or amelioration of skin aging. In particular, the disclosed invention relates to the use of PEDF-derived polypeptides for preventing and/or ameliorating skin aging.
2. Description of Related Art
Human skin, like other living tissues, ages with time. Skin aging leads to the formation of wrinkles and fine lines, thinning of the skin, skin discoloration or hyperpigmentation, and loss of firmness and elasticity. Depending on the cause, skin aging can be classified into intrinsic aging and extrinsic aging. Intrinsic aging, or chronologic aging, affects almost all internal organs, and is primarily regulated by the genetic makeup of the subject. Extrinsic aging is the result of exposure to various environmental factors, primarily ultraviolet (UV) irradiation, and hence, it is often referred to as photoaging. In the areas exposed to the sun, such as the face, neck, and backs of the hands, the combination of intrinsic aging and photoaging damage may result in changes that are more noticeable.
Collagen is a fibrous, extracellular, insoluble protein that constitutes a major component of connective tissues. Among the various types of collagen, types I and III are of major relevance. Type I collagen is the major structural protein in human skin, comprising greater than 90% of its dry weight, whereas type III collagen, also widely distributed throughout the body, predominates in fetal tissues. As the skin ages, both the overall collagen content and the ratio of type I to type III collagen declines, and the extracellular matrix (ECM) becomes disorganized. For example, both intrinsic aging and ultraviolet B (UVB) exposure diminish the renewal of collagen fibres (in particular, type I collagen). Also, UVB exposure up-regulates the production of several collagen-degrading enzymes known as matrix metaloproteinases (MMP). MMPs in humans, specifically collagenase and gelatinase, are induced within hours of UVB exposures. All those events likely result in the alteration of the dermal extracellular matrix composition.
There are many treatments available for aged skins. For example, the importance of collagen in the aging process has led to the development of many collagen-containing topical products. Other components such as retinoic acid, vitamin C and hyaluronic acid are used in cosmetics owing to the claims that they can stimulate collagen synthesis. Some cosmetic procedures (e.g., laser skin resurfacing) are also effective for reducing facial wrinkles and skin irregularities.
Despite the number of solutions that have been proposed to reduce signs of aging, or to stimulate skin renewal, none of them is capable of evoking the intrinsic repair mechanisms of the skin (i.e., collagen synthesis). In view of the foregoing, there remains a need in the art for means that effectively treats skin aging, in particular, photoaging of the skin.